1. Field of the Invention
The invention relates generally to the monitoring, servicing, and maintaining of underground electrical power lines and more specifically to a system, a tool and a method for communicating with a faulted circuit indicator using a remote display.
2. Description of Related Art
Faulted Circuit Indicators (FCIs) indicate the occurrence of a fault current in a monitored electrical conductor such as a transmission line. An FCI typically includes a housing and a number of FCI elements. The FCI elements may include a power supply such as a battery, a “remote” display for indicating when a fault in a monitored electrical conductor has occurred, a detection circuit such as a reed switch or split-core current transformer for sensing the current in the monitored electrical conductor and for providing a signal that is related to the current in the monitored conductor, and an FCI microcontroller for controlling operation of the FCI. In some cases however, the FCI may not include an FCI microcontroller.
Various types of self-powered FCIs have been constructed for detecting electrical faults in electrical conductors and the like. For example, a clamp-on type FCI clamps directly over an electrical conductor and derives its operating power from inductive and/or capacitive coupling to the monitored electrical conductor. A test point type FCIs is mounted over a test point on an electrical conductor of the power system and derives its operating power from capacitive coupling to the monitored electrical conductor. For underground electrical conductors, FCIs are generally used at padmounted distribution transformers, subsurface load centers or junction sectionalizing points (e.g., one section of an electrical conductor mates with a connector that distributes power to multiple electrical conductors). For overhead electrical conductors, FCIs are generally used at main line feeders or mid-feeder disconnects.
An FCI monitoring the status of an associated electrical conductor is typically housed in a weather-proof enclosure, either pole-mounted for overhead electrical conductors or surface-level padmounted for underground electrical conductors. Typically, the remote display (or translucent window operatively coupled to the remote display) is strategically mounted on an outside wall of the enclosure to enable easy viewing by utility personnel. Accordingly, when the enclosure is opened, utility personnel are able to access the FCI(s) and associated sections of the electrical conductor housed in the enclosure. When the enclosure is closed, the FCI(s) and associated electrical conductor sections are protected from external environmental conditions while only allowing utility personnel to view a fault condition from outside the enclosure via the remote display.
During operation of a microcontroller-based FCI, the FCI microcontroller receives the monitored current signal from the detection circuit and, based on that monitored current signal, determines the current in the electrical conductor. If the current exceeds a trip threshold setting value of the FCI, the FCI microcontroller determines that a fault condition has occurred and causes a fault condition signal to be provided to utility personnel via the remote display.
As noted above, placement of the remote display on an outside wall of the enclosure reduces the need for specially trained utility personnel to access the interior of the padmounted or the pole-mounted enclosure to determine electrical conductor status. Such a remote display may incorporate one of any number of suitable display technologies to provide an indication of electrical conductor status to the utility personnel. For example, the remote display may incorporate a mechanical target (indicator), a magnetic element, a flashing light emitting diode (LED), or a combination of technologies to display electrical conductor status to utility personnel located outside of the enclosure.
Some FCIs are designed to automatically reset at the end of a predetermined time period (e.g., eight hours) that begins when a fault condition is detected in the monitored electrical conductor. During that predetermined time period however, demand on the FCI power supply increases to enable the operation of the remote display. As a result, manual resetting of the FCI prior to expiration of the predetermined time period is often desirable. In addition to resetting the remote display, manual resetting provides an indication to the FCI microcontroller to cause it to terminate a timer countdown associated with the predetermined time period (e.g., terminates the eight hour countdown during which time an LED flashes), and thus extends the life of the FCI power supply.
For best performance, testing and maintenance activities are routinely excecuted on the FCI. Further, in some cases, the testing and maintenance activities are mandated by a number of regulatory commissions. Obviously, the time and cost associated with FCI resetting, testing and maintenance activities can be reduced if they can be performed without requiring specially trained utility personnel to open the enclosures.
To reduce the costs associated with FCI resetting, testing and other maintenance activities, U.S. Pat. No. 6,894,478 ('478), issued May 17, 2005, to Fenske, entitled “Fault Indicator with Automatically Configured Trip Settings”, discloses an FCI having a remote display configured as a “beacon bolt” mounted to an outside wall of an enclosure. The beacon bolt includes a reed switch and an LED housed in a bolt that requires a ⅝″ remote display mounting hole in the enclosure wall. Illumination and non-illumination of the LED provides the visual indication of the status of the conductor monitored by the associated FCI. The reed switch enables set/reset and test activities to be performed by the utility personnel via a magnetic test tool. The utility industry however, is migrating to a smaller remote display mounting hole (e.g., 7/16″) due to the increased ease of drilling the remote display mounting hole in the field. As a result, the ⅝″ remote display mounting hole required by the beacon bolt of the '478 patent has rendered use of the beacon bolt, with its reed switch, less desirable due to both its physical size and increased difficulty driving magnetic flux from the magnetic test tool through the beacon bolts.